本篇文章主要介绍下多线程下NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue的使用，列举几个简单的例子。
默认情况下，NSOperation并不具备封装操作的能力，必须使用它的子类，使用NSOperation子类的方式有3种：
1> 自定义子类继承NSOperation，实现内部相应的方法
2> NSBlockOperation
3>NSInvocationOperation
这讲先介绍如何用NSOperation封装一个操作，后面再结合NSOperationQueue来使用。
1.首先介绍自定义NSOperation：NSOperation是没法直接使用的，它只是提供了一个工作的基本逻辑，具体实现还是需要你通过定义自己的NSOperation子类来获得。
#import <Foundation/Foundation.h>
@protocol NSDefineOprationDelegate <NSObject>
- (void) handleDelegate;
@end
@interface NSDefineOpration : NSOperation
@property (nonatomic, assign) id <NSDefineOprationDelegate> delegate;
- (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate;
@end
实现文件里：
#import "NSDefineOpration.h"
@implementation NSDefineOpration
- (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate
{
if(self = [super init])
{
self.delegate = delegate;
}
return self;
}
- (void)main
{
@autoreleasepool {
//do something
sleep(15);
NSLog(@"op1........handle...... on thread num :%@",[NSThread currentThread]);
if([self.delegate respondsToSelector:@selector(handleDelegate)])
{
[self.delegate performSelector:@selector(handleDelegate) withObject:nil];
}
}
}
@end
这里的sleep（15）主要用来做一些延时的操作，比如网络下载等。调用：
- (void)oprationTest
{
NSDefineOpration *op1 = [[NSDefineOpration alloc] initWithDelegate:self];
op1.completionBlock = ^(){
NSLog(@"op1........OK !!");
};
[op1 start];
}
执行结果：
2017-07-25 12:07:01.051 No.22 Foundation_NSOperation[20340:1394940] op1........handle...... on thread num :<NSThread: 0x600000067c80>{number = 1, name = main}
2017-07-25 12:07:01.052 No.22 Foundation_NSOperation[20340:1395366] op1........OK !!
从执行结果可以看出，因为在实现的main函数里没有使用异步线程处理，导致直接阻塞了主线程1，所以使用这种方式一定注意main函数里操作时间过长导致主线程阻塞问题。耗时比较长的都放到其他线程里处理。
2.接下来介绍NSBlockOperation
第一种使用NSBlockOperation的方式：
NSLog(@"block start");
NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(15);
NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]);
}];
[bop2 setCompletionBlock:^{
NSLog(@"bop2........OK !!");
}];
[bop2 start];
- 第2行初始化了一个NSBlockOperation对象，它是用一个Block来封装需要执行的操作
- 第9行调用了start方法，紧接着会马上执行Block中的内容
看下执行结果：
2017-07-25 13:48:15.948 No.22 Foundation_NSOperation[20717:1441242] block start
2017-07-25 13:48:30.950 No.22 Foundation_NSOperation[20717:1441242] bop2.....handle..... on thread num<NSThread: 0x608000062780>{number = 1, name = main}
2017-07-25 13:48:30.951 No.22 Foundation_NSOperation[20717:1441598] bop2........OK !!
- 这里还是在当前线程同步执行操作，并没有异步执行，阻塞主线程。
第二种使用NSBlockOperation的方式：
- (void)blockOprationTest
{
NSLog(@"block start");
NSBlockOperation * op2 = [[NSBlockOperation alloc] init];
[op2 addExecutionBlock:^{
sleep(10);
NSLog(@"op2.....handle..... on 10 hread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(6);
NSLog(@"op2.....handle..... on 6 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(4);
NSLog(@"op2.....handle..... on 4 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(8);
NSLog(@"op2.....handle..... on 8 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(1);
NSLog(@"op2.....handle..... on 1 thread num%@",[NSThread currentThread]);
}];
[op2 setCompletionBlock:^{
NSLog(@"op2........OK !!");
}];
[op2 start];
//bop2
NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(15);
NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]);
}];
[bop2 setCompletionBlock:^{
NSLog(@"bop2........OK !!");
}];
[bop2 start];
}
执行结果：
2017-07-25 13:49:35.830 No.22 Foundation_NSOperation[20740:1443207] block start
2017-07-25 13:49:39.899 No.22 Foundation_NSOperation[20740:1443307] op2.....handle..... on 4 thread num<NSThread: 0x60800026a780>{number = 4, name = (null)}
2017-07-25 13:49:40.971 No.22 Foundation_NSOperation[20740:1443307] op2.....handle..... on 1 thread num<NSThread: 0x60800026a780>{number = 4, name = (null)}
2017-07-25 13:49:41.900 No.22 Foundation_NSOperation[20740:1443254] op2.....handle..... on 6 thread num<NSThread: 0x608000261dc0>{number = 3, name = (null)}
2017-07-25 13:49:43.902 No.22 Foundation_NSOperation[20740:1443255] op2.....handle..... on 8 thread num<NSThread: 0x60000007df80>{number = 5, name = (null)}
2017-07-25 13:49:45.832 No.22 Foundation_NSOperation[20740:1443207] op2.....handle..... on 10 hread num<NSThread: 0x60800006e780>{number = 1, name = main}
2017-07-25 13:49:45.832 No.22 Foundation_NSOperation[20740:1443255] op2........OK !!
2017-07-25 13:50:00.833 No.22 Foundation_NSOperation[20740:1443207] bop2.....handle..... on thread num<NSThread: 0x60800006e780>{number = 1, name = main}
2017-07-25 13:50:00.834 No.22 Foundation_NSOperation[20740:1443564] bop2........OK !!
分析下结果：
首先看到了有1和2两个线程，线程2在56秒的时候开始执行6秒的操作，接下来执行4，1秒结束时间为07秒。线程1在56的时候开始执行10秒的操作，接下来执行8秒，结束时间为14秒。最后执行Bop2的15秒操作至29秒。时间看起来没有问题。为什么会启用2个线程而不是3个或者更多？
3.接下来介绍NSInvocationOperation
- (void)invocationOperation
{
NSInvocationOperation * op3 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOpD) object:nil];
[op3 setCompletionBlock:^{
NSLog(@"op3........OK !!");
}];
[op3 start];
}
selector函数：
- (void)handleInvoOpD
{
sleep(5);
NSLog(@"op3.....handle..... on thread num :%@",[NSThread currentThread]);
}
执行结果：
2017-07-25 13:52:19.661 No.22 Foundation_NSOperation[20766:1446216] op3.....handle..... on thread num :<NSThread: 0x6000000662c0>{number = 1, name = main}
2017-07-25 13:52:19.662 No.22 Foundation_NSOperation[20766:1446254] op3........OK !!
NSInvocationOperation比较简单，就是继承了NSOperation，区别就是它是基于一个对象和selector来创建操作，可以直接使用而不需继承来实现自己的操作处理。
4.最后介绍下NSOperationQueue
把NSOperation子类的对象放入NSOperationQueue队列中，该队列就会启动并开始处理它。队列里可以加入很多个NSOperation, 可以把NSOperationQueue看作一个线程池，可往线程池中添加操作（NSOperation）到队列中。线程池中的线程可看作消费者，从队列中取走操作，并执行它。
实现demo：
- (void)handleOpqueue
{
NSOperationQueue *qu = [[NSOperationQueue alloc] init];
NSBlockOperation * bkOp1 = [NSBlockOperation blockOperationWithBlock:^{
sleep(10);
NSLog(@"bkOp1.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp1 setCompletionBlock:^{
NSLog(@"bkOp1........OK !!");
}];
NSBlockOperation * bkOp2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(2);
NSLog(@"bkOp2.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp2 setCompletionBlock:^{
NSLog(@"bkOp2........OK !!");
}];
NSBlockOperation * bkOp3 = [NSBlockOperation blockOperationWithBlock:^{
sleep(1);
NSLog(@"bkOp3.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp3 setCompletionBlock:^{
NSLog(@"bkOp3........OK !!");
}];
NSBlockOperation * bkOp4 = [NSBlockOperation blockOperationWithBlock:^{
sleep(10);
NSLog(@"bkOp4.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp4 setCompletionBlock:^{
NSLog(@"bkOp4........OK !!");
}];
NSBlockOperation * bkOp5 = [NSBlockOperation blockOperationWithBlock:^{
sleep(5);
NSLog(@"bkOp5.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp5 setQueuePriority:NSOperationQueuePriorityHigh];
[bkOp5 setCompletionBlock:^{
NSLog(@"bkOp5........OK !!");
}];
NSInvocationOperation *invoOp6 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOp) object:nil];
[invoOp6 setCompletionBlock:^{
NSLog(@"invoOp6........OK !!");
}];
[invoOp6 setQueuePriority:NSOperationQueuePriorityHigh];
[qu setMaxConcurrentOperationCount:2];
[qu addOperation:bkOp3];
[qu addOperation:bkOp2];
[qu addOperation:bkOp1];
[qu addOperation:bkOp4];
[qu addOperation:bkOp5];
[qu addOperation:invoOp6];
}
先看下执行结果：
2017-07-25 13:53:59.235 No.22 Foundation_NSOperation[20790:1448570] bkOp3.....handle.....on thread num<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:53:59.236 No.22 Foundation_NSOperation[20790:1448675] bkOp3........OK !!
2017-07-25 13:54:00.201 No.22 Foundation_NSOperation[20790:1448573] bkOp2.....handle.....on thread num<NSThread: 0x60800026ed80>{number = 4, name = (null)}
2017-07-25 13:54:00.202 No.22 Foundation_NSOperation[20790:1448573] bkOp2........OK !!
2017-07-25 13:54:04.311 No.22 Foundation_NSOperation[20790:1448569] bkOp5.....handle.....on thread num<NSThread: 0x6000002733c0>{number = 5, name = (null)}
2017-07-25 13:54:04.311 No.22 Foundation_NSOperation[20790:1448573] bkOp5........OK !!
2017-07-25 13:54:05.276 No.22 Foundation_NSOperation[20790:1448570] op3.....handle..... on thread num :<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:54:05.277 No.22 Foundation_NSOperation[20790:1448573] invoOp6........OK !!
2017-07-25 13:54:14.385 No.22 Foundation_NSOperation[20790:1448569] bkOp1.....handle.....on thread num<NSThread: 0x6000002733c0>{number = 5, name = (null)}
2017-07-25 13:54:14.386 No.22 Foundation_NSOperation[20790:1448573] bkOp1........OK !!
2017-07-25 13:54:15.349 No.22 Foundation_NSOperation[20790:1448570] bkOp4.....handle.....on thread num<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:54:15.350 No.22 Foundation_NSOperation[20790:1448573] bkOp4........OK !!
从结果可以看出，NSOperationQueue在2，3，4这3个线程里去处理NSOperation，而不包括主线程1。此外，在设置了bkop5以及invOp6的优先级为高时，他们会优先执行，当然这个优先时相对，是相对正在排队的，不包括已经正在执行的。
总结：NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue都比较简单，NSOperation、NSBlockOperation、NSInvocationOperation单个都是表示一种操作，而NSOperationQueue是一个可以包含多个NSOperation的队列，可以自己在多个线程处理，只要加入队列之后，我们就不用去操作，直到Callback或者完成。
